Modulation characteristics of short cavity strained-layer lasers

The low frequency response and damping behavior of four quantum well (4QW) gradedindex separate confinement heterostructure (GRINSCH) and SCH strained-layer lasers are compared. The SCH laser is shown to be better in both respects due to a shorter carrier capture time into the quantum wells. A record 3-dB bandwidth of 28 GHz is reported for a 150 pm cavity length 4QW strained-layer SCH laser. The change in the differential gain, non-linear gain coefficient, and damping rate are studied as a function of the quantum well thickness and barrier height. It is found that decreasing the well thickness does not change the non-linear gain coefficient nor the differential gain appreciably in relatively deep wells. Shallower quantum wells, however, are observed to have lower differential gain and a higher damping rate.